There are two kinds of invasive procedures that are used in the practice of pediatric cardiology: diagnostic cardiac catheterization (including angiocardiography) and catheter intervention procedures (therapeutic cardiac catheterization).
I. Cardiac Catheterization and Angiocardiography
Cardiac catheterization and angiocardiography are the definitive diagnostic tests for most cardiac patients. They are carried out under sedation or anesthesia.
Accurate diagnosis of most CHDs does not require diagnostic catheterization. With improved capability of noninvasive imaging tools such as echo and color flow Doppler studies and radiologic techniques such as cardiac magnetic resonance imaging and cardiac computed tomography, many cardiac problems are adequately diagnosed and managed without cardiac catheterization studies. Indications for these invasive studies vary from institution to institution and from cardiologist to cardiologist. The following are some circumstances that suggest the need for cardiac catheterization.
To perform balloon procedures for angioplasty (with or without stent placement), valvuloplasty, or balloon atrial septostomy in patients with lesions amenable to these procedures
To perform pulmonary valve replacement with a tissue valve (Melody valve and Edwards SAPIEN valve) that is sutured to a stent and is deployed percutaneously
To determine accurate pressure gradients in combined lesions of AS and AR or PS and PR, or multiple levels of obstruction
To assess pulmonary hypertension and its responsiveness to vasodilator therapy
To calculate pulmonary vascular resistance as a preoperative study or in the setting of low-flow lesions, such as seen in patients after bidirectional Glenn operation or after complete Fontan operation
To determine details of pulmonary vascular supply, the aortopulmonary collateral supply, and the coronary artery anatomy in patients with pulmonary atresia with intact ventricular septum or pulmonary atresia with complex ventricular anatomy
To find answers to postoperative problems such as excessive desaturation after a B-T shunt or bidirectional Glenn operation, or when excessive aortopulmonary collateral is suspected
To assess post-transplantation vasculopathy and to obtain endomyocardial biopsy for rejection identification in cardiac transplantation patients
To assess cardiomyopathy or myocarditis
To assess coronary circulation in some cases of Kawasaki disease
A number of sedatives have been used by different institutions with equal success rates. Smaller doses of sedatives are usually used in cyanotic infants. General anesthesia is usually used, especially when an interventional procedure is planned.
Among the sedatives that have been used are chloral hydrate, diphenhydramine, meperidine (Demerol), promethazine (Phenergan), chlorpromazine (Thorazine), ketamine, and morphine. It should be kept in mind that ketamine has important hemodynamic effects; it increases the SVR and blood pressure.
C. Hemodynamic Values and their Calculations
Pressure and oxygen saturation values for normal children are shown in Fig. 6.1 . During cardiac catheterization, cardiac output, cardiac shunt, and vascular resistance are routinely calculated.
Flows (cardiac output) are calculated by the Fick formula:
<SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='Pulmonaryflow(Qp)=VO2CPV−CPA,’>Pulmonaryflow(Qp)=VO2𝐶PV−𝐶PA,Pulmonaryflow(Qp)=VO2CPV−CPA,
Pulmonary flow ( Qp ) = VO 2 C PV − C PA ,
<SPAN role=presentation tabIndex=0 id=MathJax-Element-2-Frame class=MathJax style="POSITION: relative" data-mathml='Systemicflow(Qs)=VO2CAO−CMV,’>Systemicflow(Qs)=VO2𝐶AO−𝐶MV,Systemicflow(Qs)=VO2CAO−CMV,
Systemic flow ( Qs ) = VO 2 C AO − C MV ,
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